package network;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

public class UdpEchoServer {
    //1.创建一个socket对象
    private DatagramSocket socket=null;
    public UdpEchoServer(int port) throws SocketException {
        socket=new DatagramSocket(port);
    }
    public void start() throws IOException {
        System.out.println("server start!");
        // 1. 读取请求并解析. 此处 requestPacket 是 receive 的输出型参数.
        DatagramPacket requestPacket=new DatagramPacket(new byte[1024],1024);
        socket.receive(requestPacket);
        //2.此处把二进制数据转化为字符串类型
        String request=new String(requestPacket.getData(),0, requestPacket.getLength());
        //3.根据请求计算响应
        String response=process(request);
        //4.把响应传回给客户端
        DatagramPacket responsePacket=new DatagramPacket(response.getBytes(),response.getBytes().length,requestPacket.getSocketAddress());
        socket.send(responsePacket);
        //4.打印日志
        System.out.printf("[%s:%d] req: %s, resp: %s\n", requestPacket.getAddress().toString(),
                requestPacket.getPort(), request, response);
    }

    private String process(String request) {
        return request;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer udpEchoServer=new UdpEchoServer(5059);
        udpEchoServer.start();
    }
}
